Apparatus for controlling the exhaust emissions from internal combustion engines

ABSTRACT

An improved apparatus for controlling exhaust emissions and reducing the poisonous components in exhaust gases from multicylinder reciprocating and rotary piston internal combustion engines which utilizes the introduction of secondary air into the exhaust gases to further combustion thereof. A pair of exhaust collecting conduits are provided and coupled to a pulse converter which includes an inlet nozzle, a mixing tube and diffuser section. At least a portion of the pulse converter is thermally insulated so as to provide a thermally insulated reaction section wherein the exhaust gases from the engine are further reacted to control the emissions.

United States Patent Kern Mar. 19, 1974 1 APPARATUS FOR CONTROLLING THE3,059,421 10/1962 Schnabel 60/303 EXHAUST EMISSIONS FROM INTERNALCOMBUSTION ENGINES 3486326 12/1969 [76] Inventor. gfrbert Kern,Lerchenstr. 46, 7272 FOREIGN PATENTS OR APPLICATIONS tenstelg, Germany319.426 9/1929 Great Britain 60/313 Filed: g- 1 1971 805,014 11/1936France 60/323 1 PP NW 169,937 OTHER PUBLICATIONS The Oil Engine and GasTurbine," Exhaust Mani- 1 Foreign pp t Priority Data fOldS, Feb. 1952,pp. 400-401.

Dec. 9, 1970 Germany 2060630 Primary Examiner-Carlton R. Croyle [52]U.S- Cl 60/305, 60/313, Assistant Examinep-Rgbert E, Garrett 60/317,60/323 [51] Int. Cl. F02b 27/04, FOln 3/10 53 Field of Search 60/313,312, 282, 304, [57] ABSTRACT 50/323 3 7 305 307 303 An improvedapparatus for controlling exhaust emissions and reducing the poisonouscomponents in ex- [56] R f ce Ci d haust gases from multi-cylinderreciprocating and ro- UNITED STATES PATENTS tary piston internalcombustion engines which utilizes 1 455 493 17/1948 Jacobs (50/323 X theintroduction of secondary air into the exhaust 1 9 5/1958 Muller 60323gases to further combustlon there of. A pair of exhaust 3:491:5 341/1970 Gameriiiiii X313 collectmg condults are provided and coupled to a3,077,071 2/1963 Leichtfuss 60/323 x Pulse converter which includes aninlet Home, a 2,263,318 11/1941 Tifft 60/306 ing tube and diffusersection- At least a Portion 0f the 3,662,541 5/1972 s w d et 1 60/305pulse converter is thermally insulated so as to provide 3,453,824 7/1969Biesecker..... 60/313 a thermally insulated reaction section wherein theex- 3,09l,078 5/1963 Dworak.... 60/304 haust gases from the engine arefurther reacted to 3,438,198 4/1969 Bentele 60/306 control h i i3,468,124 9/1969 Hraboweckyj 60/305 3,488,723 1/1970 Veazie 60/282 16Claims, 3 Drawing Figures PATENIEDHAR 1 mm- SHEET 1 0F 2 INVENTOR:

fiERBERT KER/v PATENIEUMAR 19 m SHEET 2 OF 2 INVENTORI HERBERT KERNAPPARATUS FOR CONTROLLING THE EXHAUST EMISSIONS FROM INTERNAL COMBUSTIONENGINES BACKGROUND OF THE INVENTION In order to reduce the concentrationof carbon monoxide in the exhaust gases of internal combustioncarburetor engines having spark ignition, techniques are known whichprevent or limit the formation of carbon monoxide during combustion inthe engine, or oxidize the carbon monoxide formed during combustionoutside the engine to form carbon dioxide, and thereby render itharmless.

The formation of carbon monoxide during combustion in the engine canonly be prevented by operating with a certain amount of excess air.Since a four-stroke engine theoretically reaches its maximum meanpressure at an air ratio of 17 0.9, the actual value being somewhatlower in view of the more favorable combustion rate, extensive cleaningof the exhaust gases under all load conditions solely by means affectingthe formation of the mixture is achieved at the cost of a substantialreduction of the maximum possible performance and by poor accelerationbehavior.

When cleaning of the exhaust gases outside the engine is practiced, itis necessary to add a corresponding amount of air to the exhaust gases,irrespective of whether the oxidation of the unburnt hydrocarbons and ofthe poisonous carbon monoxide to form harmless carbon dioxide iseffected by combustion with a flame or by heterogenous catalysis. Inknown exhaust gas cleaning devices of this kind, the required air,referred to hereinafter as secondary air in distinction to the actualcombustion air of the engine, is delivered either by a separate blowerdriven by the engine, or is drawn into the exhaust conduit throughventuris. In the latter case, however, a substantial loss of performanceresults due to the increase in the static exhaust gas back pressure.

SUMMARY OF THE INVENTION It is an object of this invention to provide areliable apparatus for reducing the poisonous components in exhaustgases, which may be economically manufactured, contains no wearingparts, and causes practically no loss of performance in spite of itshigh efficiency.

Briefly stated, some of the features of the invention include anapparatus of the type hereinbefore mentioned having at least two exhaustgas collecting conduits matched in length and cross-section, and leadinginto a pulse converter consisting of inlet nozzles, a mixing pipe anddiffuser. Each of the exhaust gas collecting conduits is connected toonly those cylinders whose outlet valve opening time does notsubstantially overlap. There is provided for each exhaust gas collectingconduit at least one orifice, located immediately adja cent a cylinderand provided with means for blowing secondary air into the conduits.Further, at least the mixing tube and diffuser zone of the pulseconverter are in the form of a thermally insulated reaction section.

The features according to the invention achieve an optimum mixing of thesecondary air with the exhaust gases and the provision of the reactionsection results in a particularly effective exhaust gas cleanervirtually without increase in the exhaust gas back pressure and withoutbeing substantially affected by the prevailing operating conditions. Asa result of the combination of the exhaust gas streams near the engineand the reaction already taking place between exhaust gases andsecondary air in the collecting conduits, the components reach a veryhigh temperature, particularly in the thermally insulated zones, so thatthe reaction, additionally accelerated by the mixing process, takesplace quickly and transforms the noxious components into harmlesssubstances to the extent required.

In the embodiment where the apparatus is used with a rotary pistonengine, preferably, the secondary air inlet is within the zone of theluminous flame penetrating into the outlet during the opening of a valveor outlet slot.

It is a further object of this invention to provide an exhaust gascleaning apparatus of the kind hereinbefore mentioned, in which thereaction section is substantially rectilinear or at least curved behindthe mixing tube.

It is a further object of this invention to provide an exhaust gascleaning apparatus of the kind hereinbefore mentioned, in which thereaction section comprises the mixing and diffuser tubes and a part ofthe connected exhaust gas pipe.

It is a further object of this invention to provide an exhaust gascleaning apparatus of the kind hereinbefore mentioned, in which theelements forming the reaction section form at least one loop. Thisarrangement results in a very compact construction with the additionaladvantage of a small heat-radiating surface, which can be embedded in asimple and efficient manner in thermal insulating material. It is alsopossible to position the tube sections forming the reacting path in theform of at least one loop, so as to surround the exhaust gas collectingconduits, thus producing a particularly compact arrangement with goodheat storing properties.

It is a further object of this invention to provide an exhaust gascleaning apparatus of the kind hereinbefore mentioned, wherein the wall.separating the two inlet nozzles leading into the common mixing tube hasat least one indentation. The cross-sectional shape of this wall orpartition may be wavy, meandering or zigzag. The indentations in thewall result in particularly good mixing of the secondary air with theexhaust gases thereby furthering the reaction. In addition thereto, theexposed points of the indentations, projecting into the flow of gases,act as hot spots which reach high temperatures very quickly and insurequick starting of the exhaust gas cleaning apparatus.

It is a further object of this invention to provide an exhaust gascleaning apparatus of the kind hereinbefore mentioned, in which thepartition wall is disposed in the immediate vicinity of the outlet of acylinder in such a manner that the gases leaving the cylinder impinge onthe partition. This again achieves a very rapid heating of thepartition, which forms in this arrangement a type of baffle, while thedrawbacks relating to the increase of the exhaust gas back pressureusually encountered in the case of baffles need not be expected, in viewof the properties of the pulse converter.

It is a further object of this invention to provide an exhaust gascleaning apparatus of the kind hereinbefore mentioned, in which themixing may be further improved and the reaction accelerated by knobs orlugs projecting from the partition, or placement of inclined baffleswithin the ducting in the zone of the reaction section. These featuresalso permit a reduction in the structural length of the reaction sectionby virtue of the accelerated reaction effected by the better mixing ofexhaust gases and secondary air.

It is a further object of this invention to provide an exhaust gascleaning apparatus of the kind hereinbefore mentioned, in which thereaction section is thermally insulated by a thermal insulating materialin the form of two self-supporting half-shell moldings, or theinsulating material may be located in two supporting half-shells whichembrace the reaction section.

In principle, the apparatus according to this invention may be used forall multi-cylinder internal combustion engines including reciprocatingand rotary piston engines. For example, in an engine with two rotarypistons, corresponding to a conventional six cylinder engine, conditionsare particularly favorable for providing an exhaust gas cleaningapparatus according to one aspect of the invention in a particularlycompact arrangement.

These and other objects, advantages and features of the invention willbecome more apparent from the following description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammaticrepresentation of an exhaust gas cleaning apparatus according to thisinvention adapted for use with a six-cylinder reciprocating pistoninternal combustion engine;

FIG. 2 is a plan view of another embodiment of an exhaust gas cleaningapparatus according to this invention which includes a curved reactionsection;

FIG. 3 is a cross-sectional view of the embodiment of FIG. 2 taken alongthe line AA in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,operation of the exhaust gas system with pulse converter will first beexplained with reference to FIG. 1. The pulse converter consists of atleast two ejector-type inlet nozzles 9 leading into a common mixing tube10 and terminating in a diffuser 11. The velocity of an exhaust gas waveentering an ejector nozzle increases in accordance with the reduction ofits cross-section. Simultaneously, a part of the heat content istransformed by expansion to the pressure in the mixing tube, and theoutlet velocity of the exhaust gases from the ejector nozzle is furtherincreased. This high velocity corresponds to a low static pressure inthe mixing tube, causing exhaust gases to be induced or drawn from theejector nozzle not in use at the time, and to be mixed with the main jetin the boundary layers. The residual gas velocity remaining after themixing of the main jet and induction jet must be transformed into astatic pressure in the diffuser to enable the exhaust gases to beexpelled into the outside air through the downstream ducting. Thesuction effect of the pulse converter depends mainly on the velocity ofthe main jet and on the efficiency of the diffuser; these factors may beinfluenced by suitably dimensioning the main measurements.

The pulse converter is so connected to the exhaust gas collectingconduits 7, 8 of the engine that the two ejector nozzles 9 are affectedalternately and in regular sequence by exhaust gas pressure waves, inaccordance with the ignition timing. For example, in the sixcylinderengine shown in FIG. 1, those cylinders having an ignition timing of 240are connected to a common exhaust pipe. With an assumed firing order of1, 5, 3, 6, 2, 4, cylinders l, 2, 3 are connected to one collectingconduit 7, and cylinders 4, 5, 6 into the other collecting conduit 8. Inthis manner, the pressure wave passing from cylinder 1 into thecollecting conduit 7 produces through the pulse converter a suction wavein the conduit 8, while the pressure wave passing from cylinder 5 intothe collecting conduit 8 produces a suction wave in the conduit 7, whichfollows the pressure wave in cylinder 1. Since the major part of thephase shift between a pressure wave and the following suction wavedepends on the ignition timing, the position of the suction wave is onlyslightly affected by the rotational speed.

According to the invention, a thermal insulation 23 surrounds that partof the mixing tube, diffuser, and exhaust conduit designated as thereaction section as well as the exhaust gas collecting conduits 7, 8.

Orifices 22, shown diagrammatically in the drawing, are provided in theimmediate vicinity of the cylinder outlets for blowing in secondary air.Preferably this secondary air is blown in by a conventional blower, theconnections of which are indicated diagrammatically at 26. The secondaryair, which is heated on its path to the nozzles 9 in the conduits 7 and8 and starts to react with the exhaust gases under further heating, isagain intensively mixed with the exhaust gases in the mixing tube 10 andin the diffuser 11, and is further heated by the reaction already takingplace; during this, the desired transformation of the noxiousconstituents in the exhaust gases into harmless constitutents occurs andthe waste gases leaving the reaction section, constructed as a heatreservoir, contain a very low and acceptable proportion of noxioussubstances.

It should be noted that the partition 24 is in the immediate vicinity ofthe cylinder 6 and receives the direct impact of the gases leaving thiscylinder, thereby acting as a baffle. Partition 24 is therefore heatedvery quickly and acts as a hot spot accelerating the reaction. It shouldbe noted that partition 24 may have a curved configuration in crosssection or along its longitudinal axis. Further, partition 24 may haveformed thereon projecting members, indentations or any other conceivableconfiguration that would assist in acceleration of reaction of gases.

Adjustable baffles may be provided in the portion of the reactionsection surrounded by thermal insulation 23, in order to furtherintensify the mixing of exhaust gases and secondary air, with theconsequence that the reaction is accelerated, allowing for a shorterreaction section to achieve the desired degree of exhaust gas cleaning;this is of particular advantage if the exhaust gas cleaning system is tobe used in existing equipment.

FIG. 2 shows an embodiment of the exhaust gas cleaning apparatusaccording to the invention, in which the reaction section, formed by themixing tube 10, the diffuser ll and a part of the exhaust conduit 12,has a curved configuration. The exhaust collecting conduits 7 and 8terminate in the form of ejectors in the mixing tube and form inletnozzles, not shown in the drawing.

To produce a compact space saving construction, the reaction sectionwith the connected exhaust pipe 12 forms a loop arranged adjacent theexhaust gas collecting conduits 7, d to achieve quick heating.

The portions of the loop 110, l i, 112 and a part of the exhaust gascollecting conduits '7, d are enclosed in a heat insulating material,located in two half-shells, one of which is indicated at ll7.Cylindrical mounting sleeves are provided in the half-shells, as at 2%,21 enabling the whole device to be installed, easily, for example, bymeans of screws or bolts after assembly.

The configuration of the two half-shells l7, l3 and their adaptation tothe shape of the exhaust gas cleaning device of FIG. 2 is seen in thesection shown in FIG. 3. Sufficient space 19 is provided between theconduits carrying the gases and the half-shells 17, Mi, wherein a heatinsulating material may be placed. if desired, this thermal insulatingmaterial may itself carry out the function of the half-shells shown inthis embodiment by constructing it as a molding of suitableconfiguration and of sufficient strength.

The embodiment shown in FIGS. 2 and 3 of an exhaust gas cleaning deviceis particularly suitable for an engine diagrammatically indicated byreference numeral 30, with two rotary pistons and features a compactconstruction and high efficiency with practically no loss inperformance.

Although the above description is directed to preferred embodiments ofthe invention, it is noted that other variations and modifications willbe apparent to those skilled in the art and, therefore, may be madewithout departing from the spirit and scope of the present invention.

What is claimed is:

1. An apparatus for controlling the exhaust emissions from an internalcombustion engine the combination comprising: a pair of exhaustcollecting conduits each being positioned to collect exhaust gasses fromthe internal combustion engine in a timing sequence such that exhaustgasses enter one of said conduits at a time when exhaust gasses do notenter the other of said conduits; a pulse converter which includes apair of inlet nozzles having a common wall, a mixing tube and adiffuser, said diffuser being coupled to an exhaust pipe, said inletnozzles being coupled to said pair of exhaust collecting conduits;positive pressure means for blowing secondary air in the immediatevicinity of each cylinder outlet prior to entry into the exhaustcollecting conduits and for initiating the reaction of said exhaustgases; said exhaust pipe including a reaction section at its endimmediately adjacent the pulse converter; and means for thermallyinsulating at least a portion of said exhaust collecting conduits, theentire pulse converter and the entire reaction section, whereby theprimary mixing of said secondary air with said exhaust gases takes placewithin said pulse converter, and the primary reaction of the exhaustgases takes place within said diffuser and said reaction section.

2. An apparatus as set forth in claim 1., wherein said internalcombustion engine is a cylinder piston type having cylinders with apredetermined ignition firing I order, one half of said cylinders beingcoupled to one of said pair of exhaust collecting conduits and theremaining half being coupled to the other in a predetermined manner sothat exhaust gases are discharged alternately into each of therespective exhaust collecting conduits.

3. An apparatus as set forth in claim 1, wherein said pair of exhaustcollecting conduits are substantially balanced in length and crosssection.

4. An apparatus as set forth in claim 1, wherein said internalcombustion engine is a rotary piston type and wherein said means forintroducing secondary air comprises a blower coupled to said exhaustcollecting conduits in a manner so that secondary air is introduced intoa zone of luminous flame extending beyond a valve during the openingthereof.

5. An apparatus as set forth in claim ll wherein said reaction sectionincludes in addition to said mixing tube and diffuser, a portion of anexhaust pipe coupled to the diffuser outlet end, which reaction sectionis substantially rectilinear.

6. An apparatus as set forth in claim ll wherein said reaction sectionhas a curved configuration along its axis at least after the mixingtube.

7. An apparatus as set forth in claim 6 wherein said reaction section isformed in the shape of a loop with a portion of the reaction sectionadjacent said exhaust collecting conduits being of a smaller diameterthan that of its outlet end.

d. An apparatus as set forth in claim 7 wherein said looped reactionsection contains a portion thereof disposed about said exhaustcollecting conduits in order to achieve rapid heating thereof.

9. An apparatus as set forth in claim ll wherein said pair of exhaustcollecting conduits include an elongated conduit having a first volumefor a portion thereof and a second volume greater than that of saidfirst volume for the remaining portion thereof, a partition walldisposed in said portion having said second volume so as to form a pairof adjacent exhaust collecting conduits, said wall terminating adjacentsaid inlet nozzles.

10. An apparatus as set forth in claim 9 wherein said partition wallextends at one end thereof into said inlet nozzles, the latter eachhaving progressively decreasing cross-sectional areas in the down-streamdirection.

lll. An apparatus as set forth in claim 9 wherein said partition wall isdisposed adjacent the outlet of at least one cylinder so that the gasesissuing from the cylinder impinge on said wall.

12. An apparatus as set forth in claim 1 which further includes aplurality of baffle plates disposed in said reaction section.

llB. An apparatus as set forth in claim 1, wherein said means forthermally insulating are in the form of two self-supporting half-shellmoldings adapted to be con nected to one another.

14. An apparatus as set forth in claim l which further includes asupporting shell disposed about at least the sections having saidthermal insulating means disposed thereabout, thereby providingmechanical relief for conduit sections subjected to high thermalstresses.

15. An apparatus for controlling the exhaust emissions from asix-cylinder engine having the cylinders arranged in a straight line thecombination comprising: a pair of exhaust collecting conduits each beingcoupled to one half of the cylinders of the engine in a predeterminedmanner so that the exhaust gases are discharged alternately into each ofthe respective exhaust collecting conduits, said pair of exhaustcollecting conduits including a substantially straight elongated tubularconduit having a first diameter for a portion thereof and a seconddiameter greater than that of said first diameter for the remainingportion thereof, a partition wall disposed in said portion having saidsecond diameter so as to form a pair of adjacent exhaust collectingconduits; a pulse converter section which includes a pair of inletnozzles, a mixing tube and diffuser, said inlet nozzles ends thereofbeing coupled to said pair of exhaust collecting conduits at the endhaving said second diameter; positive pressure means for introducingsecondary air in the immediate vicinity of each cylinder outlet; andmeans for thermally insulating at least a portion of said exhaustcollecting conduits, said pulse converter and at least a portion of saidexhaust pipeso as to form a thermally insulated reaction section whereinthe exhaust gases from the engine are reacted in order to control theexhaust emissions therefrom.

16. An apparatus for controlling the exhaust emissions from a rotarypiston engine the combination comprising: a pair of tubular exhaustcollecting conduits each being coupled to the engine in a predeterminedmanner so that the exhaust gases are discharged alternately into each ofthe respective exhaust collecting conduits; a reaction section includinga mixing tube and diffuser portion, said mixing tube being incommunication with each of said pair of exhaust collecting conduits,said reaction section being further characterized in that it is in alooped configuration with the portion thereof coupled to said exhaustcollecting conduits being of a smaller diameter than that of the outletend thereof; positive pressure means for introducing secondary air inthe immediate vicinity of each rotary piston exhaust outlet; and meansfor thermally insulating said reaction section so as to form a thermallyinsulated reaction section wherein the exhaust gases from the engine arereacted in order to control the exhaust emissions therefrom.

1. An apparatus for controlling the exhaust emissions from an internalcombustion engine the combination comprising: a pair of exhaustcollecting conduits each being positioned to collect exhaust gasses fromthe internal combustion engine in a timing sequence such that exhaustgasses enter one of said conduits at a time when exhaust gasses do notenter the other of said conduits; a pulse converter which includes apair of inlet nozzles having a common wall, a mixing tube and adiffuser, said diffuser being coupled to an exhaust pipe, said inletnozzles being coupled to said pair of exhaust collecting conduits;positive pressure means for blowing secondary air in the immediatevicinity of each cylinder outlet prior to entry into the exhaustcollecting conduits and for initiating the reaction of said exhaustgases; said exhaust pipe including a reaction section at its endimmediately adjacent the pulse converter; and means for thermallyinsulating at least a portion of said exhaust collecting conduits, theentire pulse converter and the entire reaction section, whereby theprimary mixing of said secondary air with said exhaust gases takes placewithin said pulse converter, and the primary reaction of the exhaustgases takes place within said diffuser and said reaction section.
 2. Anapparatus as set forth in claim 1, wherein said internal combustionengine is a cylinder piston type having cylinders with a predeterminedignition firing order, one half of said cylinders being coupled to oneof said pair of exhaust collecting conduits and the remaining half beingcoupled to the other in a predetermined manner so that exhaust gases aredischarged alternately into each of the respective exhaust collectingconduits.
 3. An apparatus as set forth in claim 1, wherein said pair ofexhaust collecting conduits are substantially balanced in length andcross section.
 4. An apparatus as set forth in claim 1, wherein saidinternal combustion engine is a rotary piston type and wherein saidmeans for introducing secondary air comprises a blower coupled to saidexhaust collecting conduits in a manner so that secondary air isintroduced into a zone of luminous flame extending beyond a valve duringthe opening thereof.
 5. An apparatus as set forth in claim 1 whereinsaid reaction section includes in addition to said mixing tube anddiffuser, a portion of an exhaust pipe coupled to the diffuser outletend, which reaction section is substantially rectilinear.
 6. Anapparatus as set forth in claim 1 wherein said reaction section has acurved configuration along its axis at least after the mixing tube. 7.An apparatus as set forth in claim 6 wherein said reaction section isformed in the shape of a loop with a portion of the reaction sectionadjacent said exhaust collecting conduits being of a smaller diameterthan that of its outlet end.
 8. An apparatus as set forth in claim 7wherein said looped reaction section contains a portion thereof disposedabout said exhaust collecting conduits in order to achieve rapid heatingthereof.
 9. An apparatus as set forth in claim 1 wherein said pair ofexhaust collecting conduits include an elongated conduit having a firstvolume for a portion thereof and a second volume greater than that ofsaid first Volume for the remaining portion thereof, a partition walldisposed in said portion having said second volume so as to form a pairof adjacent exhaust collecting conduits, said wall terminating adjacentsaid inlet nozzles.
 10. An apparatus as set forth in claim 9 whereinsaid partition wall extends at one end thereof into said inlet nozzles,the latter each having progressively decreasing cross-sectional areas inthe down-stream direction.
 11. An apparatus as set forth in claim 9wherein said partition wall is disposed adjacent the outlet of at leastone cylinder so that the gases issuing from the cylinder impinge on saidwall.
 12. An apparatus as set forth in claim 1 which further includes aplurality of baffle plates disposed in said reaction section.
 13. Anapparatus as set forth in claim 1, wherein said means for thermallyinsulating are in the form of two self-supporting half-shell moldingsadapted to be connected to one another.
 14. An apparatus as set forth inclaim 1 which further includes a supporting shell disposed about atleast the sections having said thermal insulating means disposedthereabout, thereby providing mechanical relief for conduit sectionssubjected to high thermal stresses.
 15. An apparatus for controlling theexhaust emissions from a six-cylinder engine having the cylindersarranged in a straight line the combination comprising: a pair ofexhaust collecting conduits each being coupled to one half of thecylinders of the engine in a predetermined manner so that the exhaustgases are discharged alternately into each of the respective exhaustcollecting conduits, said pair of exhaust collecting conduits includinga substantially straight elongated tubular conduit having a firstdiameter for a portion thereof and a second diameter greater than thatof said first diameter for the remaining portion thereof, a partitionwall disposed in said portion having said second diameter so as to forma pair of adjacent exhaust collecting conduits; a pulse convertersection which includes a pair of inlet nozzles, a mixing tube anddiffuser, said inlet nozzles ends thereof being coupled to said pair ofexhaust collecting conduits at the end having said second diameter;positive pressure means for introducing secondary air in the immediatevicinity of each cylinder outlet; and means for thermally insulating atleast a portion of said exhaust collecting conduits, said pulseconverter and at least a portion of said exhaust pipe so as to form athermally insulated reaction section wherein the exhaust gases from theengine are reacted in order to control the exhaust emissions therefrom.16. An apparatus for controlling the exhaust emissions from a rotarypiston engine the combination comprising: a pair of tubular exhaustcollecting conduits each being coupled to the engine in a predeterminedmanner so that the exhaust gases are discharged alternately into each ofthe respective exhaust collecting conduits; a reaction section includinga mixing tube and diffuser portion, said mixing tube being incommunication with each of said pair of exhaust collecting conduits,said reaction section being further characterized in that it is in alooped configuration with the portion thereof coupled to said exhaustcollecting conduits being of a smaller diameter than that of the outletend thereof; positive pressure means for introducing secondary air inthe immediate vicinity of each rotary piston exhaust outlet; and meansfor thermally insulating said reaction section so as to form a thermallyinsulated reaction section wherein the exhaust gases from the engine arereacted in order to control the exhaust emissions therefrom.